okay more on this... still looking for a solution on this.
One thought is glass mount antenna that stays in the car. Like this but I'm concerned about window tinting and they suggest putting it on the windshield.
I'm still not sure where the OEM assist antenna is. There is an antenna in the glass on the drivers side rear quarter, but I'm not sure if that is a radio antenna or not.

I'm also considering ordering an OEM BMW shark fin antenna and putting it on the roof, although I would much rather go with something stealth or low profile. SF antenna is like $60 from Crevier and I would have to get it painted... not sure how much cable it comes with (if any).
Anyone have any suggestions?